Acanthamoeba ingests both digestible particles (yeast) and indigestible particles (latex beads) readily. Experiments to test whether internal processing of digestible and indigestible particles is also similar showed that the cell has mechanisms for distinguishing particle quality and with the appropriate stimulus can rid itself more rapidly of indigestible particles. These experiments are part of a continuing study of cellular controls on endocytosis. In studies on another eucaryote, Saccharomyces cerevisiae, long term objectives are to understand the spatial and temporal control of chitin synthase activity during the cell cycle. An examination of seven temperature sensitive mutants blocked in various stages of the cell cycle has shown that mutants blocked in early stages of the cell cycle synthesize abnormally high amounts of chitin and show a loss of spatial restriction of the sites of synthesis.